What would cause a fuel gauge to peg way past full?

[IndyShiftman]

I purchased one of these:

Here is a description:
"1st time ever - a new complete injection fuel tank manufactured to factory specs. No cutting, no seams other than factory professional manufacturing. This tank utilizes the factory tank with new electric pump in tank that produces 85-115 PSI at 50-60 gallons per hour. It will allow you to use any late model fuel injection motor. This tank is ready to go, designed to work with any 12 volt system, and sending unit is designed for any factory applications. Manufactured with correct fuel neck and fittings. Includes fuel sender, fuel pump, strainer, lock ring & O ring. All of our fuel injection tanks have a baffle on the inside. These tanks may be in stock, but may take up to 2 weeks to receive. Fits 67 68 GM F-body cars Camaro / Firebird / Trans Am models. This is not a universal tank."


Problem is, my fuel gauge pegs way past full now with it installed.
There are 4 wires. Two black wires on a single ring terminal. A gray wire, and a purple wire.
There was no instructions. So I know the blacks are ground. I took a battery connected the black wires to - post. Touched the purple to the + and didn't hear the pump running so I then touched the gray wire to + and the fuel pump started working.
So my connections have my original sending unit wire (tan) connected to the purple, the pump signal wire to the gray and the grounds are grounded to the body. And the fuel pump is working. with it all connected. But my gauge is pegged now. :-\

I hope there is an easy solution.

[Rendid]

Re: What would cause a fuel gauge to peg way past full?

Take an ohmmeter and see what the resitance is between ground wire and the purple wire.
If the tank is empty, it should read around 0, if it's full, about 90 ohms.
If that's right, then check the wiring going to the gauge for excessive resistance.

[squirrel]

Re: What would cause a fuel gauge to peg way past full?

being disconnected will do it! also many GM gages read way past full when the tank is full, that's just the way they are. We have 2 that are really bad like that....mostly it's the ones made in the past 40 years that do it!

[joe_rocket45]

Re: What would cause a fuel gauge to peg way past full?

it's hooked up right, but the purple wire is for the late model vehicles (87 up I think) ...they may not be the ohms, I'd do the same as Jim said and see if it starts working when the fuel is lower. I went through this on a Blazer once and it would read full when a little over 1/2" tank.

[fabricatordave]

Re: What would cause a fuel gauge to peg way past full?

if you put 12 v power through sender you may have cooked it check purp to ground with ohm meter 0 empty 90 full or other way around?if shows open circut sender is f-ed up

[IndyShiftman]

Re: What would cause a fuel gauge to peg way past full?

I think Dave is correct. It's showing open circuit. :-[
I think the company that puts these together should be responsible since it didn't come with any connection diagram or instructions. But I know it's my fault.

Thanks for the replies everyone.

[squirrel]

Re: What would cause a fuel gauge to peg way past full?

That's a bummer. It's usually a better idea to figure out which wire is which using an ohm meter than by putting power to them. But it's even better to have them labeled in the first place, which the company failed to do. I'd suggest you blame them, hopefully you can raise enough stink that they'll start to label the wires, even if they don't give you a new sender.

[70.5CAMARO]

Re: What would cause a fuel gauge to peg way past full?

did you tear into it to make sure it just wasnt loose or disconnected write on the sender itself or maybe the float is stuck past full not even touching the contacts, If i read right you didnt have to open it up at all, it came fully assembled, and the grey is most definatley pump and purple is gauge, i would definatley check ground resistance between the loop and the frame, just to make sure, cause that big of a pump should have its own ground right in the loom all the way to a central grounding location to instill a good ground.

[Scott Liggett]

Re: What would cause a fuel gauge to peg way past full?

Generally, if your gauge is reading past full and the tank isn't full, it's the positive wire that has a connection problem. If it's reading totally empty, it's the ground.

If your tank if full of gas right now; I'd drive it for a while and see what happens. If the gauge doesn't ever move, then recheck your wiring. You'll want to run most of the gas out of it before you drop the tank again anyways. Much lighter that way.

[IndyShiftman]

Re: What would cause a fuel gauge to peg way past full?

The gauge pegged when the tank was totally dry. Filled it yesterday and obviously it reads full but still pegged off the scale.
When I applied voltage to the sender wire, I did hear a tick. But I thought it may have been nothing.
On the plus side, I called The Paddock Restoration Parts and the manufacturer. They agreed to FedEx a new sending unit next week free of charge. So even if I do find a bad connection, I'll have an extra sending unit.

[HoosierGTA]

Re: What would cause a fuel gauge to peg way past full?

Not quite free of charge,you worked for it! I had the same problem with my daughters pick-up .I re-did the wires and extended them(their never long enough) well I didn't have red and black wires so after I got done putting the tank back in........er.....I forgot which was hot and ground. I got lucky!

[70.5CAMARO]

Re: What would cause a fuel gauge to peg way past full?

now you did work for it, you have to remove and reinstall it, and use all that gas- thats the fun part though

[min301]

Re: What would cause a fuel gauge to peg way past full?

LOL, no thats only for us, we don't pay for the gas we use up. ;D

[HoosierGTA]

Re: What would cause a fuel gauge to peg way past full?


If you need someone to come get the gas out just let me know... hah.

[Monster]

Re: What would cause a fuel gauge to peg way past full?

Just had the same problem with my Chevy II. The fuel guage pegged way past full.
It was an open circuit.
Good luck.